Riverside Gardens is part of the £15bn Nine Elms on the South Bank regeneration and was created via an unusual collaboration between Lambeth and Wandsworth Councils and the developers St George.
The 2000sq m park is situated in Wandsworth but was paid for by Section 106 planning provision negotiated by Lambeth and St George.
The leaders of Wandsworth and Lambeth Councils, councillor Govindia and Peck respectively and St George managing director Michael Bryn-Jones, officially launched the park on Monday with a plaque unveiling.
Riverside Gardens replaces an unused and difficult to access area and gives users views of the River Thames and Battersea Power Station as well as giving access to the river.
Pocket parks are a key part of the vision for the area.
Councillor Peck, who is also co-chair of the Nine Elms Vauxhall Partnership said: "Open spaces are an important part of our ambitions for the area. Riverside Gardens is the first of many green spaces which will transform this stretch of the South Bank into a greener and more vibrant part of central London."